Klarinet Archive - Posting 000466.txt from 2001/02

From: Tony@-----.uk (Tony Pay)
Subj: Re: [kl] Difference Tones
Date: Mon, 12 Feb 2001 19:21:01 -0500

On Mon, 12 Feb 2001 18:05:39 -0500, bhausmann1@-----.com said:

> At 02:23 PM 2/12/2001 +0000, Tony Pay wrote:

> > I know Bill Hausmann is worried about the organ stop that makes the
> > walls of his church 'shake'. But whatever the explanation of this
> > is, it can't be due to the production of a lower frequency
> > *perception* by the addition of a higher pipe (as was sometimes done
> > in early pipe organs).
> >
> > Perhaps his organ uses a more modern technique. An electronic
> > device called a ring modulator produces real sum and difference
> > tones from two inputs, but I don't know whether that technique is
> > ever used in organs.
> >
> > In order to have any idea at all, I want to know more about the
> > 'shaking'. Is it a space resonance on certain notes, or noticeable
> > at all pitches? How do you detect it, Bill, with your hand?
>
> I only know about this organ from a recording. But you can check it
> out yourself more easily than I can, Tony. The recording was made in
> Liverpool Cathedral! The 16 Hz 32-foot CCCC, in combination with
> another pipe a 5th above it produces a resultant bass note that can be
> measured, recorded, seen on an oscilloscope, and FELT as a 8 Hz
> 64-foot CCCCC. The waves in the grooves on the LP disc (recorded
> digitally, but cut on an analog disc in 1979) on a separate sample 8
> Hz CCCCC can be clearly SEEN on the vinyl with the naked eye. That's
> why I am having so much trouble with this "perception" thing, even
> though I doubt that my stereo does the recording any justice at all.

Well, I don't understand this. The only thing I can think of at the
moment is that the walls or other parts of the Cathedral respond
non-linearly, and thus generate heterodyne frequencies that are then
recorded by the microphones, in the same way that the inner ear responds
non-linearly, and generates our perceptions of difference tones.

I'll ask around.

Tony
--
_________ Tony Pay
|ony:-) 79 Southmoor Rd Tony@-----.uk
| |ay Oxford OX2 6RE GMN artist: http://www.gmn.com
tel/fax 01865 553339

... Divers do it deeper.

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